1. Field of the Invention
The present invention relates generally to solid electrolytic capacitors.
2. Description of the Background Art
In recent years a variety of techniques have been proposed to reduce solid electrolytic capacitors in equivalent series resistance (ESR).
Japanese Patent Laying-open No. 2004-247665 discloses a solid electrolytic capacitor including a capacitor element, a cathode lead frame, and a supporting cathode lead frame. The cathode lead frame is connected to the capacitor element and at least partially exposed from an exterior of resin. The supporting cathode lead frame is connected to the capacitor element and the cathode lead frame. The cathode lead frame and the supporting cathode lead frame are laser-welded and thus interconnected.
Japanese Patent Laying-open No. 2002-246268 discloses a solid electrolytic capacitor including a capacitor element, an exterior of resin, a metal layer, and a lead frame. The lead frame is electrically connected to the capacitor element and at least partially exposed from the exterior of resin. The metal layer sandwiches the capacitor element, and via the metal layer the capacitor element and the lead frame are electrically connected therebetween. For connection, an electrically conductive adhesive is used, for example.
A capacitor element is sandwiched by a lead terminal attached in a method for example as described in Japanese Patent Laying-open No. 9-266137, as follows: the capacitor element is initially placed on a cathode lead terminal and bonded with silver paste. Subsequently, the capacitor element is bonded to a portion of the cathode lead terminal that is folded back with silver paste.
According to Japanese Patent Laying-open No. 2004-247665, when there is variation in production and a capacitor element is increased in thickness, the cathode lead frame and the supporting cathode lead frame are spaced by an increased distance and may thus not be welded together. This results in reduced production yield.
According to Japanese Patent Laying-open No. 2002-246268, it is necessary to provide a lead frame for electrical connection between an external portion of the capacitor and the metal layer. This results in increased production cost.
Furthermore, for a mass production process, in particular, it is necessary to rapidly transfer to a designated place a product having an electrically conductive adhesive applied thereto. In doing so, as the electrically conductive adhesive is unset, the metal layer may be displaced from a predetermined position. This results in reduced production yield.
According to Japanese Patent Laying-open No. 9-266137, the cathode lead terminal sandwiching the capacitor element exerts excessive pressure to the capacitor element and may thus damage the capacitor element. This results in the solid electrolytic capacitor's reduced production yield and impaired reliability.
Furthermore, this pressure may squeeze the silver paste out from between the cathode lead terminal and the capacitor element and as a result the cathode lead terminal and an anode can short-circuit. This decreases the solid electrolytic capacitor's production yield and reliability.